Allow SSO iFrames — chaptergy

This plugin changes HTTP headers to allow websites to be iframed which block this. It is meant for development and testing purposes.
It does the following:

• Drop all 'x-frame-options' response headers
• Drop all 'content-security-policy' response headers
• Change all 'set-cookie' response headers to set 'SameSite=None' (this also requires the Secure flag to be set for the cookie)
• Change 'sec-fetch-dest' request headers to 'document' if it equals 'iframe'

Note, that when cookies within this iframe are required, the iframe content has to be HTTPS, otherwise cookies will not be set.